Grinding apparatus of the traveling belt type



July 5, 1955 w. D. ROBERTS GRINDING APPARATUS OF THE TRAVELING BELT TYPE 2 Sheets-Sheet 1 l l l l l l lu Filed Aug. 22, 1952 mum s T my R EiNNNIQNWE: mp. m Hfi u a.

July 5, 1955 w. D. ROBERTS GRINDING APPARATUS OF THE TRAVELING BELT TYPE Filed Aug. 22, 1952 2 Shuts-Sheet 2 (/1 IN VEN TOR.

144. ram 0. P085. 2 1- BY E nv-v-ozzws r United States Patent GRINDING APPARATUS OF THE TRAVELING BELT TYPE William D. Roberts, Pittsburgh, Pa., assignor t0 Ryman Engineering Company, Ellwood City, Pa., :1 corporation of Pennsylvania Application August 22, 1952, Serial No. 305,784

3 Claims. (Cl. 51-135) This invention relates to grinding apparatus of the sanding belt type, and more particularly to abrading belts that are driven by a driver belt that has frictional engagement with the abrasive belt, the belts respectively being mounted on separate pairs of pulleys. The present invention is an improvement upon or addition to that disclosed in my application Serial No. 284,556, filed April 26, 1952 (now Patent 2,692,460).

In grinding articles of curved contour by the use of sanding belts, it frequently is the case that the higher areas of a convex surface become abraded too much relative to the lower areas. In the case of small articles such as turbine blades, accuracy to within -.005 inch plus or minus is required, and it is difiicult to secure such accuracy. A similar situation exists in the grinding of the concave sides of the blades, in that there is tendency for too great grinding away of the metal at the edges of the blade.

This invention has for its object the provision of an arrangement wherein the driving belt for the sanding belt is so positioned with respect thereto that the tension on the sanding belt is relieved as it approaches the work holder, and the major portion of the driving force is exerted on the sanding belt by the driver over a limited area after it has passed the work holder.

In the accompanying drawings,

Figure 1 is a side elevational view of a machine embodying my invention, in partly schematic form;

Fig. 2 is a sectional view, on an enlarged scale, of the driving pulley of Fig. 1;

Fig. 3 is an enlarged sectional view through a work piece such as that shown in Figs. 1 and 6;

Fig. 4 is a view taken on the line IV-IV of Fig. 3;

Fig. 5 is an end view of two of the tracking rolls of Fig. 1, and their associated guide roll;

Fig. 6 is a face view thereof, and

Fig. 7 is a view showing a modified form of apparatus, wherein the sanding belt is engaged in grinding the concave side of a work piece.

The apparatus as shown in the drawings difiers from that disclosed in my said application mainly in the manner in which the sanding belt is driven and tension thereon is greatly reduced as it approaches the work piece, there being also herein shown certain tracking arrangements for guiding the belt as it passes the work holder.

The apparatus is shown as mounted in a framework 10 that may be superimposed upon the base that is shown and described in my said application. A driving pulley 11 is driven from a suitable motor by a belt 12. A driver belt 13 for a sanding belt 14 extends around the driven pulley 11 and an idler pulley 16. The belt 14 extends around pulleys 17 and 18 and its upper run is in frictional engagement with the belt 13, so that the sanding belt will be driven by the driving belt. The pulley 17 can suitably be mounted in adjustable bearings, so that it can be positioned closer to the pulley 11, thus giving a greater extent of Wrap around with respect to the lower run of the belt 13, thereby increasing the frictional driving the friction against the work 2,712,204 Patented July 5, 1955 area. Grooved guide pulleys 19 and 20 are provided for the belt 13. This belt may be grooved and ribbed throughout its length, as shown at 21.

A work holder is indicated generally at 22 and comprises an upper die member 23 and a lower die member 24, the die members respectively serving to guide the sanding belt to the convex and concave contours of a work piece 25 (Figs. 1-347), as explained more fully in my co-pending application.

As shown in Figs. 1 and 3, the sanding belt 14 is being moved across the convex side of the work piece 25 in order to grind the same to the desired shape.

The frictional driving force of the belt 13 will be exerted upon the belt 14 mainly at the pulley 17, although the lower run of the belt 13 will have some relatively light engagement with the belt 14 along the upper run of 14. Guide pulleys 27 and 28 are provided near the end of the lower run of the belt 13 and are adjustable vertically, so that the pulley 27 can hold the belt 21 entirely out of engagement with the belt 14, at the pulley .18, or only lightly in engagement, as may be desired. This light engagement of the belt 13 with the belt 14 will reduce tendency of floating or hunting of 14 on the pulley 18.

The lighter frictional drag on the upper run of the belt 14 by the belt 13 after leaving the pulley 17, will reduce tensional stress on the belt 14 at points between the pulley 18 and the work holder 22. Therefore, the stress on the sanding belt at the workholder is not so great as to cause excessive grinding of the higher areas of the work piece 25, which is where the greatest pressure on the work piece would ordinarily occur.

A similar situation exists when the belt is directed against the concave side of the work piece, except that piece would ordinarily be greatest near its edges.

The guide pulleys 27 and 28 are journaled in a bracket 29 which has vertical adjustment by a pin-and-slot arrangement at 3031, so that the lower run of the belt 13 can be adjusted vertically relative to the pulley 18 and hence be engaged against the belt 14 with a desired degree of pressure at the pulley 18, or entirely disengaged therefrom, to insure adequate easing of friction and tension in the lower run of the belt 14 after it passes the pulley 18.

The bearings for the pulley 18 are mounted in a bracket 32 that is adjustable about a vertical axis, by a worm gear adjustment'33, to insure proper angularity of the puliey 18. Likewise, the pulleys 16 and 2728 are carried by a bracket 34 that is angularly adjustable about a vertical axis. The brackets for pulleys 16 and 18 are shiftable by means of pistons in air cylinders 35 and 36 respectively, to provide desired tensions on the belts. These features are described in detail in my said application.

The pressure in the air cylinder 35 may be as much as lbs. per square inch, and the pressure in the cyla inder 36 may be as low as 8 ounces, the purpose being to have the belt 13 under adequate tension for the required frictional driving force and the sanding belt 14 under relatively light tension, so that when the lower run of the sanding belt is flexed or deflected at the work holder to engage the surface of the work piece, the sanding belt 14 at that portion between the pulley 18 and the work holder 22 will, in effect, yield or be shifted against the slight tensional force in the cylinder 36.

While the lower run of the sanding belt 14 may pass directly from the pulley 18 to the work .holder 22 and thence to the pulley 17 without any guiding or tracking devices, for some classes of work, I here show a track or guide device for insuring that the belt will be maintained in accurate alignment with the work piece 25 and so that the edges of the belt will not rub against the sides or the upstanding ribs at the .ends of the work piece.

To this end, I show a pair of tracking rollers 37 and 38 together with a guide roller 39 past which the belt 14 is drawn as it approaches the work holder, Also, a tracking roller '40 and a guide roller 41 are provided at the exit side of the work holder. These tracking rollers 37-38-4*0 may be of various conventional forms such as shown 'in Figs. and 6, to insure that any slight lateral deviations will immediately and automatically be cor rected.

In Figs. 5 and '6, I show the manner in which the tracking rollers 37 and 38 and the guide roller 39 are mounted upon the bracket arm 42. 'These rollers are carried by abracket 43 that is held in rotatably adjusted positions on the bracket arm 42 by a set screw 44. The rollers 37 and 38 are on eccentrically adjustable shafts 45 that are held in adjusted positions in the bracket 43 by setscrews 46. The two sections of each of the rolls 3'7 and 38 are angularly disposed with respect to each other, so that their frustro-conical surfaces tend to maintain the belt 14 in centralized position thereon, because as the belt creeps one way or the other, one edge will have the tensional force thereon relieved, so that higher tensioned edges will pull the belt back to its correct position, as is well known with devices of this character. Adjustment of the eccentrically-mounted shafts 45 is initially as in Fig. 5 wherein the zero or neutral points 47 of-the rolls 3'] and 38 are at positions about mid way of the wrap around areas of the sanding belts upon these rolls. The tracking roll 40 and the guide roll 41 may be suitably mounted on brackets similar to the brackets 42 and 4-3.

Other forms of devices for maintaining the belt in a desired path-may be employed, such as for example the scanning tube apparatus shown in my said application.

Although the two belts 13-17 are here shown as mounted on pulleys whose axes are horizontal, it will be understood that the apparatus could be turned so that the axes of the pulleys are vertical, the position of the belts,'of course, being correspondingly changed,

The tracking rolls 373840, as well as the guide rolls 39 and 41, are idlers, in that they are rotated by the frictional drag of the sanding belt.

In-Fig. 7, which shows the work piece in cross section, a:

for purpose "of clarity, the sanding belt 14 is being employed to grind the concave side of the work piece, the lower run of the belt just before it reaches the work holder 22 being under but little tension as heretofore explained.

In this form of device, the belt is guided in an accurate path past the work piece, by an electronic scanningtube 51 that is mounted adjacent to an edge of the belt and controls electrical circuits that operate beltguiding or shifting devices as explained in detail in my said application.

I claim as my invention:

1. A surfacing machine of the sanding-belt type, comprising a pair of relatively-spaced pulleys, a looped surfacing belt supported thereby, a looped driver belt disposed against the outer face of one run of the surfacing belt, pulleys forthe driver belt spaced farther apart than fit) the surfacing belt pulleys and in partly opposed relation thereto at the remote faces of the surfacing belt pulleys, whereby one run of the driver belt is held deflected toward the other run thereof and in partly embracing relation to the surfacing belt and its pulleys, the deflected run of the driver belt being held in frictional engagement with the adjacent run of the sanding belt, with greater pressure near one end of the sanding belt loop than at the other end of said loop.

2. A surfacing machine of the sanding-belt type, comprising a pair of relatively-spaced pulleys, a looped surfacing belt supported thereby, a looped driver belt disposed against the outer face of one run of the surfacing belt, pulleys for the driver belt spaced farther apart than the surfacing belt pulleys and in partly opposed relation thereto at the remote faces of the surfacing belt pulleys, whereby one run of the driver belt is held deflected toward the other run thereof and in partly embracing relation to the surfacing belt and its pulleys, the deflected run of the driver belt being held in frictional engagement with the adjacent run of the sanding belt, with greater pressure near one end of the sanding belt loop than at the other end of said loop, and means for varying the frictional drag between the two belt loops at the last-named end thereof, independently of the frictional driving force exerted at the other end of the sanding belt loop.

3. A surfacing machine of the sanding-belt type, comprising a pair of relativelyspaced pulleys, a looped surfacing belt supported thereby, a looped driver belt disposed against the outer face of one run of the surfacing belt, pulleys for the driver belt spaced farther apart than the surfacing belt pulleys and in partly opposed relation thereto at the remote faces of the surfacing belt pulleys, whereby one run of the driver belt is held deflected toward the other run thereof and in partly embracing relation to the surfacing belt and its pulleys, the deflected run-of'the driver belt being held in frictional engagement with the adjacent run of the sanding belt, with greater pressure near one end of the sanding belt loop than at the other end of said loops, a work holder disposed "in proximity to the other run of the abrasive belt, and means disposed between the said holder and one of the sanding belt pulleys for automatically correcting lateral deflections of the belt from the desired path of travel past the work holder.

References Cited in the file of this patent UNITED .STATES PATENTS 1,043,194 Blevney Nov. 5, 19.12 1,244,310 Freeman Oct. 23, 1917 1,288,908 Johnson Dec. 24, 1918 1,656,958 Seel Jan. 24, 1928 1,791,288 Schweitzer Feb. 3, 1931 1,972,075 Clark Sept. 4, 1934 2,274,268 Hercik Feb. 24, 1942 2,279,782 Fowler Apr. 14, 1942 2,479,506 Payton Aug. 16,1949 2,575,656 Coe et al Nov. 20, 1951 2,587,603 Czarnecki Mar. 4, 1952 2,597,256 Murray :May 20, 1952 

